An existing touch display device usually comprises a liquid crystal display panel, and a touch panel arranged on the liquid crystal display panel.
The liquid crystal display panel is mainly formed by assembling an array substrate and a color filter substrate. The array substrate is provided thereon with gate lines and data lines which are arranged to intersect in a grid form (the gate line and the data line are located in different layers, and thus are not electrically connected with each other while intersecting). The gate lines and the data lines intersect to define pixel units, and each pixel unit comprises a thin film transistor, a pixel electrode connected with a drain of the thin film transistor, and a common electrode. Gates of the thin film transistors of the pixel units in one row are connected with the same gate line, and sources of the thin film transistors of the pixel units in one column are connected with the same data line. When a gate line is activated, only by controlling a signal of each data line, the row of pixel units corresponding to said gate line can display desired content at the same time. Therefore, only by activating (also called scanning) all the gate lines in turn, a display screen of the display device can display desired content. The touch panel comprises a first sensing line and a second sensing line which intersect and are insulated from each other, wherein a first coupling capacitance is generated in an overlap position of the first sensing line and the common electrode; a second coupling capacitance is generated in an overlap position of the second sensing line and the common electrode; and a by-pass capacitance is generated at an intersection point of the first sensing line and the second sensing line, and a touch position is determined by detecting change in the by-pass capacitance.
The inventors have found that at least the following problem exists in the prior art: after a row of pixel units are scanned, a potential on the gate line that turns on said row of pixel units is changed from a high potential to a low potential (or from a low potential to a high potential), and a data voltage signal applied from a data line to the pixel unit corresponding thereto will jump at the moment of said change. The jump of the data voltage signal on said data line will cause a common voltage signal on the common electrode to have a spike pulse. Said change in the common voltage signal on the common electrode will lead to changes in the first coupling capacitance, the second coupling capacitance and the by-pass capacitance, and further result in inaccurate detection of the touch position.